For insertion of a catheter into a biological lumen such as digestive tract and blood vessel, a guide wire is employed to lead the catheter to a desired position in the lumen. When in use, the guide wire is passed through the catheter.
The guide wire is also employed to lead the catheter, which is inserted into an endoscope or its lumen, to a desired position of the biological lumen being observed or treated through the endoscope.
Among guide wires proposed so far is one disclosed in U.S. Pat. No. 5,379,779. The disclosed guide wire includes a core and a coating layer covering the surface thereof, the core having the main body and the distal end part extending from the main body. This guide wire has a heat-shrinkable tube of fluoroplastic resin as its coating layer which reduces frictional resistance and improves slidability, thereby making the guide wire easier to handle.
However, the guide wire mentioned above, which is covered with a heat-shrinkable tube as the coating layer, exhibits poor adhesion between the core and the heat-shrinkable tube. Thus, when the guide wire is turned in the presence of a comparatively large load, only the heat-shrinkable tube turns, and torque is not transmitted to the core. Moreover, the heat-shrinkable tube of fluoroplastic resin is comparatively expensive and is not so low in frictional resistance.
To address this problem, it has been proposed to form the covering layer mentioned above from a fluoroplastic resin. The resulting guide wire includes a core, a distal covering layer which covers the distal end part of the core and is formed from a flexible material, and a main body covering layer which covers the main body of the core and is formed from a fluoroplastic resin. The covering layers are formed such that the rear end of the distal covering layer overlaps the distal end of the main body covering layer, so that the core does not expose itself.
This guide wire construction exhibits poor adhesion between the distal covering layer and the main body covering layer and so the former easily peels off from the latter.